Curium radioactivity

Each of the elements has a number of isotopes (2,4), all radioactive and some of which can be obtained in isotopicaHy pure form. More than 200 in number and mosdy synthetic in origin, they are produced by neutron or charged-particle induced transmutations (2,4). The known radioactive isotopes are distributed among the 15 elements approximately as follows actinium and thorium, 25 each protactinium, 20 uranium, neptunium, plutonium, americium, curium, californium, einsteinium, and fermium, 15 each herkelium, mendelevium, nobehum, and lawrencium, 10 each. There is frequently a need for values to be assigned for the atomic weights of the actinide elements. Any precise experimental work would require a value for the isotope or isotopic mixture being used, but where there is a purely formal demand for atomic weights, mass numbers that are chosen on the basis of half-life and availabiUty have customarily been used. A Hst of these is provided in Table 1. 

Most chemical iavestigations with plutonium to date have been performed with Pu, but the isotopes Pu and Pu (produced by iatensive neutron irradiation of plutonium) are more suitable for such work because of their longer half-Hves and consequendy lower specific activities. Much work on the chemical properties of americium has been carried out with Am, which is also difficult to handle because of its relatively high specific alpha radioactivity, about 7 x 10 alpha particles/(mg-min). The isotope Am has a specific alpha activity about twenty times less than Am and is thus a more attractive isotope for chemical iavestigations. Much of the earher work with curium used the isotopes and Cm, but the heavier isotopes... 

These elements have all been named for famous scientists or for the places of their creation. For example, americium, berkelium, and californium were named after obvious geographical locations. Nobelium was named for the Nobel Institute, although later study proved it was not really created there. Curium was named for Marie Curie, the discoverer of radium. Einsteinium was named for the famous physicist, Albert Einstein. Fermium and lawrencium were named for Enrico Fermi and Ernest O. Lawrence, who made important discoveries in the field of radioactivity. Mendelevium was named for the discoverer of the periodic chart. 

ISOTOPES There are 23 isotopes of curium. All of them are man-made and radioactive. The most stable is curium-247, with a half-life of 1.56xl0+ years (156,600,000 years), which through alpha decay transmutates into plutonium-243. 

Curium metal and its compounds are radioactive bone-seeking poisons that attack the skeletal system of humans and animals. Care must be used in handling them. 

ISOTOPES There are a total of 21 isotopes of californium. None are found in nature and all are artificially produced and radioactive. Their half-lives range from 45 nanoseconds for californium-246 to 898 years for californium-251, which is its most stable isotope and which decays into curium-247 either though spontaneous fission or by alpha decay. 

Symbol Cm atomic number 96 atomic weight 247 a radioactive transuranium actinide series element electron configuration [Rn]5/ 6di7s2 most stable valence state +3 most stable isotope Cm-247. Curium isotopes, half-hves and decay modes are ... 

The Mars Pathfinder rover carried an Alpha Proton X-ray Spectrometer (APXS), and the two Mars Exploration Rovers (MER - Spirit and Opportunity) carried Alpha Particle X-ray Spectrometers (also called APXS, but in this case more precise versions of the Pathfinder instrument, though without the ability to monitor protons for light element analyses). These instruments contained radioactive curium sources (Fig. 13.16) whose decay produced a-particles, which irradiated target rocks and soils. The resulting characteristic X-rays provided measurements of major and minor element abundances. The MER rovers also carried Mossbauer spectrometers, which yielded information on iron oxidation state. 

Pancam image of the end of the MER arm, showing its APXS (used for chemical analyses) and RAT (used for abrading or brushing rock surfaces). A photograph of the APXS (bottom) shows radioactive curium a-particle sources surrounded by detectors. 

All Mars rovers to date have carried alpha-particle X-ray spectrometer (APXS) instruments for chemical analyses of rocks and soils (see Fig. 13.16). The source consists of radioactive curium, which decays with a short half-life to produce a-particles, which then irradiate the sample. Secondary X-rays characteristic of specific elements are then released and measured by a silicon drift detector. The Mars Pathfinder APXS also measured the backscattered a-particles, for detection of light elements, but the Mars Exploration Rovers measured only the X-rays. 

CURIUM. CAS 7440-51-9], Chemical element- symbol Cm. at. no. 96, at. wt. 247 (mass number of the most stable isotope i, radioactive metal of the Actinide series, also one of Ihe Transuranium elements, mp estimated 1350 50 C. l7CTn has a half-life of 1.64 x It)7 years, Olher long-lived isotopes arc J,Cm (ti j =9320 years), 4, Cm = 54X0 years I. "Cm... 

After a few years of storage, the main radioactive heat emitters in HLW are 90Sr and 137Cs. In addition, extremely long-lived actinides—neptunium, plutonium, americium, and curium—should be collected for transmutation in the future. Therefore, different flowsheets can be proposed for waste processing. It is possible to extract each radionuclide in the special extraction (sorption) cycle, for example, uranium and plutonium in the PUREX process, and after that, minor actinides (MAs) by the TRUEX process,4 strontium by the SREX process,5,6 and cesium by sorption7 or extraction.8... 

Among the artificial radioactive elements of which Seaborg was discoverer or co-discoverer are Americium, Curium, Berkelium, Californium, and Scaborgium. 

Since the uranyl ion is so obviously its own category, it is very interesting to compare with the analogous species formed by transuranium elements. M = Np, Pu and Am form all three MO 72 and MO which are, by no means, the most stable oxidation states of their elements, and which tend toward reduction by the radiochemical products concomitant with the high specific radioactivity of the isotopes normally studied of plutonium and americium (whereas e.g. 244Pu with the half-life 82 million years would not present this problem). Contrary to some reports in literature, it does not seem that curium (and the subsequent elements) form such dioxo complexes. 

The thermal neutron sources are radioactive isotopes which emit neutrons, acclerators, and nuclear reactors. The neutrons from the sources are moderated with materials such as paraffin, graphite, water, heavy water or beryllium. Some of the radioisotopes used as sources of thermal neutrons are antimony, polonium, americium curium and californium. The various sources have different half-lives, ranging from days to years. 

Protactinium is silvery and relatively unreactive, but actinium and curium are so radioactive that they glpw. Neptunium is similar to uranium and plutonium in appearance. Americium is similar and is very electropositive, dissolving readily in acids to give the Am3+ ion. 

Solid curium compounds are known, e.g., CmF3, CmF4, CmCl3, CmBr3, white Cm203 (mp 2265°C), and black Cm02. Where X-ray structural studies have been made— and these are difficult, since amounts of the order of 0.5 pg must be used to avoid fogging of the film by radioactivity and because of the destruction of the lattice by emitted particles—the compounds are isomorphous with other actinide compounds. 

This isotope slowly undergoes radioactive decomposition, with emission of alpha particles. Its half-life is 500 years. Curium is made from... 

Actinides in the environment can be classified into two groups (i) the uranium and thorium series of radionuclides in the natural environment and (ii) neptunium, plutonium, americium and curium which are formed in a nuclear reactor during the neutron bombardment of uranium through a series of neutron capture and radioactive decay reactions. Transuranics thus produced have been spread widely in the atmosphere, geosphere and aquatic environment on the earth, as a result of nuclear bomb tests in the atmosphere, and accidental release from nuclear facilities (Sakanoue, 1987). Most of these radionuclide inventories have deposited in the northern hemisphere following the tests conducted by the United States and the Soviet Union. 

The first samples of curium were so small they could be detected only by the radiation they gave off In 1947, the first significant sample of the element was produced. It weighed about 30 milligrams, or the equivalent of about one-thousandth of an ounce. The element was named for Polish-French physicist Marie Curie (1867-1934) and her husband, French physicist Pierre Curie (1859-1906). The Curies carried out some of the earliest research on radioactive elements. 

Curium was named after Polish-French physicists Marie and Pierre Curie, who conducted research on radioactive elements. 

All 21 known isotopes of curium are radioactive. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element s name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. 

The curium isotope with the longest half life is curium-247. Its half life is 15.6 million years. The half life of a radioactive element is the time it takes for half of a sample of the element to break down. After about 15.6 million years, only 0.5 grams of the isotope would remain from a one-gram sample produced today. The other 0.5 gram would have changed into another element. 

Clinical management can potentially reduce the effects of plutonium intake, although the effectiveness can be highly variable. Administration of the calcium salt of diethylenetriaminepentaacetic acid (DTPA) can accelerate removal of soluble forms of plutonium from body fluids and recent deposits. It is unable to remove intracellular deposits or activity buried in bone and must therefore be administered as soon as possible after an intake. In a review of 18 patients exposed to plutonium, americium, or curium, the US Food and Drug Administration concluded that administration of 1 g Ca-DTPA in 5 ml sterile aqueous solution, either by intravenous injection or as a nebulized inhalation dose, increased the rate of radioactivity elimination in urine by an average of 39-fold. Daily maintenance doses of Zn-DTPA resulted in continued elimination of radioactivity. 

First, the trivalent actinide and lanthanide elements are separated from the other elements in the waste. In the second step, americium and curium are then separated from the lanthanide elements. Experimental studies have largely been laboratory-scale in which synthetic waste solutions and tracer levels of radioactivity were utilized. A few laboratory-scale experiments were made in hot cells on the coextraction of trivalent actinides and lanthanides. The two most promising methods investigated for co-removal of trivalent actinides and lanthanides are ... 

---